# 文本左右对齐

<div class="notranslate">
  <p>给定一个单词数组和一个长度&nbsp;<em>maxWidth</em>，重新排版单词，使其成为每行恰好有&nbsp;<em>maxWidth</em>&nbsp;个字符，且左右两端对齐的文本。</p>

  <p>你应该使用“贪心算法”来放置给定的单词；也就是说，尽可能多地往每行中放置单词。必要时可用空格&nbsp;<code>' '</code>&nbsp;填充，使得每行恰好有 <em>maxWidth</em>&nbsp;个字符。
  </p>

  <p>要求尽可能均匀分配单词间的空格数量。如果某一行单词间的空格不能均匀分配，则左侧放置的空格数要多于右侧的空格数。</p>

  <p>文本的最后一行应为左对齐，且单词之间不插入<strong>额外的</strong>空格。</p>

  <p><strong>说明:</strong></p>

  <ul>
    <li>单词是指由非空格字符组成的字符序列。</li>
    <li>每个单词的长度大于 0，小于等于&nbsp;<em>maxWidth</em>。</li>
    <li>输入单词数组 <code>words</code>&nbsp;至少包含一个单词。</li>
  </ul>

  <p><strong>示例:</strong></p>

  <pre><strong>输入:</strong>
    words = ["This", "is", "an", "example", "of", "text", "justification."]
    maxWidth = 16
<strong>输出:</strong>
    [
    &nbsp; &nbsp;"This &nbsp; &nbsp;is &nbsp; &nbsp;an",
    &nbsp; &nbsp;"example &nbsp;of text",
    &nbsp; &nbsp;"justification. &nbsp;"
    ]
    </pre>

  <p><strong>示例&nbsp;2:</strong></p>

  <pre><strong>输入:</strong>
    words = ["What","must","be","acknowledgment","shall","be"]
    maxWidth = 16
<strong>输出:</strong>
    [
    &nbsp; "What &nbsp; must &nbsp; be",
    &nbsp; "acknowledgment &nbsp;",
    &nbsp; "shall be &nbsp; &nbsp; &nbsp; &nbsp;"
    ]
<strong>解释: </strong>注意最后一行的格式应为 "shall be    " 而不是 "shall     be"
    因为最后一行应为左对齐，而不是左右两端对齐，第二行同样为左对齐，这是因为这行只包含一个单词。
    </pre>

  <p><strong>示例&nbsp;3:</strong></p>

  <pre><strong>输入:</strong>
    words = ["Science","is","what","we","understand","well","enough","to","explain",
    &nbsp;        "to","a","computer.","Art","is","everything","else","we","do"]
    maxWidth = 20
<strong>输出:</strong>
    [
    &nbsp; "Science &nbsp;is &nbsp;what we",
      "understand &nbsp; &nbsp; &nbsp;well",
    &nbsp; "enough to explain to",
    &nbsp; "a &nbsp;computer. &nbsp;Art is",
    &nbsp; "everything &nbsp;else &nbsp;we",
    &nbsp; "do &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"
    ]
    </pre>
</div>

以下程序实现了这一功能，请你填补空白处内容：

```java
class Solution {
	public List<String> fullJustify(String[] words, int maxWidth) {
		List<String> ret = new ArrayList<>();
		int index = 0;
		while (index < words.length) {
			int cur = index, len = 0;
			while (cur < words.length && len + words[cur].length() + cur - index <= maxWidth) {
				len = len + words[cur++].length();
			}
			cur--;
			StringBuilder sb = new StringBuilder();
			if (cur == words.length - 1) {
				for (int i = index; i <= cur; i++) {
					sb.append(words[i]);
					if (i < cur) {
						sb.append(' ');
					}
				}
			} else {
				int base = cur > index ? (maxWidth - len) / (cur - index) : (maxWidth - len);
				String baseStr = genSpace(base);
				int left = cur > index ? (maxWidth - len) % (cur - index) : 0;
				String leftStr = genSpace(base + 1);
				for (int i = index; i <= cur; i++) {
					sb.append(words[i]);
          ___________________;
				}
			}
			if (sb.length() < maxWidth) {
				sb.append(genSpace(maxWidth - sb.length()));
			}
			ret.add(sb.toString());
			index = cur + 1;
		}
		return ret;
	}
	private String genSpace(int n) {
		char[] cs = new char[n];
		Arrays.fill(cs, ' ');
		return new String(cs);
	}
}
```

## template

```java
class Solution {
	public List<String> fullJustify(String[] words, int maxWidth) {
		List<String> ret = new ArrayList<>();
		int index = 0;
		while (index < words.length) {
			int cur = index, len = 0;
			while (cur < words.length && len + words[cur].length() + cur - index <= maxWidth) {
				len = len + words[cur++].length();
			}
			cur--;
			StringBuilder sb = new StringBuilder();
			if (cur == words.length - 1) {
				for (int i = index; i <= cur; i++) {
					sb.append(words[i]);
					if (i < cur) {
						sb.append(' ');
					}
				}
			} else {
				int base = cur > index ? (maxWidth - len) / (cur - index) : (maxWidth - len);
				String baseStr = genSpace(base);
				int left = cur > index ? (maxWidth - len) % (cur - index) : 0;
				String leftStr = genSpace(base + 1);
				for (int i = index; i <= cur; i++) {
					sb.append(words[i]);
					if (i < cur) {
						sb.append(left > 0 ? leftStr : baseStr);
						left--;
					}
				}
			}
			if (sb.length() < maxWidth) {
				sb.append(genSpace(maxWidth - sb.length()));
			}
			ret.add(sb.toString());
			index = cur + 1;
		}
		return ret;
	}
	private String genSpace(int n) {
		char[] cs = new char[n];
		Arrays.fill(cs, ' ');
		return new String(cs);
	}
}
```

## 答案

```java
if (i < cur) {
  sb.append(left > 0 ? leftStr : baseStr);
  left--;
}
```

## 选项

### A

```java
if (i < cur) {
  sb.append(left > 0 ? baseStr : leftStr);
  left--;
}
```

### B

```java
if (i < cur) {
  sb.append(left > 0 ? baseStr : leftStr);
  left++;
}
```

### C

```java
if (i < cur) {
  sb.append(left >= 0 ? leftStr : baseStr);
  left--;
}
```